Electric storage apparatus and manufacturing method of electric storage apparatus

ABSTRACT

An electric storage apparatus has a positive electrode plate, a negative electrode plate, and a separator. Each of the positive electrode plate and the negative electrode plate has a collector plate and an active material layer containing an electrolytic solution, and the active material layer is formed in a predetermined width on a partial region of a collector plate. The separator is placed between the positive electrode plate and the negative electrode plate and contains an electrolytic solution. At least one of the positive electrode plate and the negative electrode plate, an edge of the active material layer in a width direction has a waveform. A set value Wn of the width of the active material layer and a variation ΔW of the width of the active material layer satisfy a condition of 0.03≦ΔW/Wn≦0.056.

TECHNICAL FIELD

The present invention relates to an electric storage apparatus havingelectrodes each including an active material layer formed on a surfaceof a collector plate, and to a manufacturing method of the electricstorage apparatus.

BACKGROUND ART

A secondary battery has a positive electrode plate, a negative electrodeplate, and a separator placed between the positive electrode plate andthe negative electrode plate. The positive electrode plate has acollector plate and a positive electrode active material layer formed ona surface of the collector plate. The negative electrode plate has acollector plate and a negative electrode active material layer formed ona surface of the collector plate.

In forming the positive electrode plate or the negative electrode plate,the collector plate is formed as a long length of sheet, and theconstituent material of the active material layer is applied onto thecollector plate along its longitudinal direction. The width of theactive material layer is smaller than the width of the collector plate,and a partial region of the collector plate is not covered with theactive material layer. The collector plate having the active materiallayer formed thereon can be cut into predetermined lengths to providepositive electrode plates or negative electrode plates.

PRIOR ART DOCUMENT Patent Document

[Patent Document 1] Japanese Patent Laid-Open No. 11 (1999)-162516

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In the application of the constituent material of the active materiallayer onto the collector plate, the width of the active material layermay vary. The variations in the width of the active material layer maycause variations in the capacities of the manufactured secondarybatteries or may influence the capacities of the secondary batteries.

Means for Solving the Problems

An electric storage apparatus according to a first aspect of the presentinvention has a positive electrode plate, a negative electrode plate,and a separator. Each of the positive electrode plate and the negativeelectrode plate has a collector plate and an active material layercontaining an electrolytic solution, and the active material layer isformed in a predetermined width on a partial region of a collectorplate. The separator is placed between the positive electrode plate andthe negative electrode plate and contains an electrolytic solution. Atleast one of the positive electrode plate and the negative electrodeplate, an edge of the active material layer in a width direction has awaveform. A set value Wn of the width of the active material layer and avariation ΔW of the width of the active material layer satisfy acondition of the following expression (I):

0.03≦ΔW/Wn≦0.056   (I)

According to the first aspect of the present invention, the ratio(ΔW/Wn) is set to be equal to or lower than 0.056 in the state in whichthe waveform is produced on the edge of the active material layer,thereby enabling suppression of a reduction in the capacity of theelectric storage apparatus. In addition, the ratio (ΔW/Wn) can be set tobe equal to or higher than 0.03 to suppress a deviation of the capacityof the electric storage apparatus from the capacities of the otherelectric storage apparatuses.

The width of the active material layer of the negative electrode platecan be larger than the width of the active material layer of thepositive electrode plate. In this case, the active material layer of thenegative electrode plate can be set to satisfy the condition of theexpression (I). The region of the active material layer of the negativeelectrode plate that is opposed to the active material layer of thepositive electrode plate corresponds to the region in which a chemicalreaction is performed in charge and discharge of the electric storageapparatus. Thus, the region in which the chemical reaction is performedis located not to be adjacent to the edge of the active material layer,which can prevent the edge of the active material layer from adverselyaffecting the charge and discharge of the electric storage apparatus.

The edge can be formed at a position in the collector plate that isadjacent to the region in which the active material layer is not formed.In this edge, the waveform satisfying the expression (I) can be formedeasily.

A method of manufacturing an electric storage apparatus according to asecond aspect of the present invention has the three steps. At a firststep, an active material layer is formed in a predetermined width on apartial region of a collector plate to manufacture a positive electrodeplate and a negative electrode plate. At a second step, a separator isplaced between the positive electrode plate and the negative electrodeplate. At a third step, the active material layer in each of thepositive electrode plate and the negative electrode plate and theseparator are impregnated with an electrolytic solution.

At the first step, in manufacturing at least one of the positiveelectrode plate and the negative electrode plate, a waveform is formedon an edge of the active material layer in a width direction. A setvalue Wn of the width of the active material layer and a variation ΔW ofthe width of the active material layer are set to satisfy a condition ofthe following expression (II):

0.03≦ΔW/Wn≦0.056   (II)

According to the second aspect of the present invention, the ratio(ΔW/Wn) is set to be equal to or lower than 0.056 in the state in whichthe waveform is produced on the edge of the active material layer,thereby enabling suppression of a reduction in the capacity of theelectric storage apparatus. In addition, the ratio (ΔW/Wn) can be set tobe equal to or higher than 0.03 to suppress variations in capacity amonga plurality of electric storage apparatuses.

A constituent material of the active material layer can be applied ontoa surface of the collector plate by a die coater. The die coaterreleases the constituent material of the active material layer to thecollector plate. The variation ΔW can be adjusted by changing thedistance between the die coater and the collector plate. Thus, the ratio(ΔW/Wn) can be easily adjusted so as to satisfy the condition of theexpression (II).

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] A schematic diagram showing the internal structure of a cell.

[FIG. 2] A developed view of a power-generating element.

[FIG. 3] A section view of a positive electrode, a negative electrode,and a separator.

[FIG. 4] An enlarged view showing an edge of a negative electrode activematerial layer.

[FIG. 5] A graph showing the relationship among a variation of the widthof the negative electrode active material layer, a variation of capacityin cells, and a capacity in cells.

MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will hereinafter be described.

Embodiment 1

A cell (corresponding to an electric storage apparatus) which isEmbodiment 1 of the present invention is described with reference toFIG. 1. FIG. 1 is a schematic diagram showing the internal structure ofthe cell. A secondary battery such as a nickel metal hydride battery anda lithium-ion battery can be used as the cell 1. Instead of thesecondary battery, an electric double layer capacitor can be used.

The cell 1 can be mounted on a vehicle, for example. Specifically, aplurality of cells 11 can be used to constitute an assembled batterywhich can be mounted on the vehicle. The plurality of cells 1 can beconnected electrically in series or connected electrically in parallel.

The assembled battery can be used as a power source for running of thevehicle. When an electric energy output from the assembled battery isconverted into a kinetic energy by a motor generator, the kinetic energycan be used to run the vehicle. For decelerating or stopping thevehicle, the motor generator can convert a kinetic energy produced inbraking of the vehicle into an electric energy. The electric energygenerated by the motor generator can be stored as regenerative power inthe assembled battery.

The cell 1 has a cell case 10 and a power-generating element 30 housedin the cell case 10. The cell case 10 can be made of metal, for example,and has a case body 11 and a lid 12. The case body 11 has an openingportion for inserting the power-generating element 30, and the lid 12closes the opening portion of the case body 11. The lid 12 is fixed tothe case body 11 to seal the cell case 10 hermetically. The case body 11and the lid 12 can be fixed to each other, for example by welding.

A positive electrode terminal 21 and a negative electrode terminal 22are fixed to the lid 12 and protrude toward the outside of the cell case10. A positive electrode tab 23 is connected to the positive electrodeterminal 21 and the power-generating element 30 to connect the positiveelectrode terminal 21 electrically to the power-generating element 30.The positive electrode tab 23 can be provided as a component separatefrom the positive electrode terminal 21 or provided integrally with thepositive electrode terminal 21. A negative electrode tab 24 is connectedto the negative electrode terminal 22 and the power-generating element30 to connect the negative electrode terminal 22 electrically to thepower-generating element 30. The negative electrode tab 24 can beprovided as a component separate from the negative electrode terminal 22or provided integrally with the negative electrode terminal 22.

FIG. 2 is a developed view of the power-generating element 30. FIG. 2shows part of the power-generating element 30.

The power-generating element 30 is an element for performing charge anddischarge and has a positive electrode plate 31, a negative electrodeplate 32, and a separator 33. The positive electrode plate 31 has acollector plate 31 a and a positive electrode active material layer 31 bformed on a surface of the collector plate 31 a. The positive electrodeactive material layer 31 b contains a positive electrode activematerial, a conductive material, a binder and the like. When thelithium-ion secondary battery is used as the cell 1, examples of thepositive electrode active material can include LiCoO₂, LiMn₂O₄, LiNiO₂,LiFePO₄, Li₂FePO₄F, LiCo_(1/3)Ni_(1/3)Mn_(1/3)O₂, and Li(Li_(a)Ni_(x)Mn_(y)CO_(z))O₂. Examples of the material of the collectorplate 31 a can include aluminum.

The positive electrode active material layer 31 b covers a partialregion of the collector plate 31 a. In other words, one end portion ofthe collector plate 31 a is not covered with the positive electrodeactive material layer 31 b and is exposed to the outside. The positiveelectrode active material layer 31 b can be formed on the surface of thecollector plate 31 a by using an application apparatus such as a diecoater and a gravure coater.

The negative electrode plate 32 has a collector plate 32 a and anegative electrode active material layer 32 b formed on a surface of thecollector plate 32 a. The negative electrode active material layer 32 bcontains a negative electrode active material, a conductive material, abinder and the like. When the lithium-ion secondary battery is used asthe cell 1, examples of the negative electrode active material caninclude amorphous graphite. Examples of the material of the collectorplate 32 a can include copper.

The negative electrode active material layer 32 b covers a partialregion of the collector plate 32 a. In other words, one end portion ofthe collector plate 32 a is not covered with the negative electrodeactive material layer 32 b and is exposed to the outside. The negativeelectrode active material layer 32 b can be formed on the surface of thecollector plate 32 a by using an application apparatus such as a diecoater and a gravure coater. The positive electrode active materiallayer 31 b, the negative electrode active material layer 32 b, and theseparator 33 are impregnated with an electrolytic solution. When thelithium-ion secondary battery is used as the cell 1, examples of theelectrolytic solution can include a mixture of LiPF₆ and a solventcontaining mixed EC (Ethylene Carbonate), DMC (Dimethyl Carbonate), andEMC (Ethyl Methyl Carbonate).

The positive electrode plate 31, the negative electrode plate 32, andthe separator 33 are stacked in the order shown in FIG. 2, and the stackis wound to provide the power-generating element 30. The region of thecollector plate 31 a that is not covered with the positive electrodeactive material layer 31 b is connected to the positive electrode tab 23(see FIG. 1). This electrically connects the positive electrode plate 31of the power-generating element 30 to the positive electrode terminal21. The region of the collector plate 32 a that is not covered with thenegative electrode active material layer 32 b is connected to thenegative electrode tab 24 (see FIG. 1). This electrically connects thenegative electrode plate 32 of the power-generating element 30 to thenegative electrode terminal 22.

The cell 1 of the present embodiment is of a so-called square type inwhich the power-generating element 30 is housed in the cell case 10formed to conform to a rectangle. In addition to the cell of the squaretype, a so-called cylindrical type of cell can be used as the cell 1. Inthe cylindrical type of cell, the power-generating element is housed ina cell case having a cylindrical shape. The configuration of thepower-generating element in the cylindrical type of cell is the same asthat shown in FIG. 2.

FIG. 3 is a section view of the positive electrode plate 31, thenegative electrode plate 32, and the separator 33. Specifically, FIG. 3is a diagram when the positive electrode plate 31, the negativeelectrode plate 32, and the separator 33 are cut in a plane orthogonalto the longitudinal direction (left-right direction of FIG. 2) of thepositive electrode plate 31, the negative electrode plate 32, and theseparator 33.

As shown in FIG. 3, the positive electrode active material layer 31 b isformed on each of the surfaces of the collector plate 31 a, and thenegative electrode active material layer 32 b is formed on each of thesurfaces of the collector plate 32 a. The separator 33 is placed betweenthe positive electrode active material layer 31 b and the negativeelectrode active material layer 32 b and is in contact with the positiveelectrode active material layer 31 b and the negative electrode activematerial layer 32 b.

While the positive electrode active material layer 31 b is formed oneach of the surfaces of the collector plate 31 a and the negativeelectrode active material layer 32 b is formed on each of the surfacesof the collector plate 32 a in the present embodiment, the presentinvention is not limited thereto. Specifically, it is possible to use anelectrode (so-called bipolar electrode) in which the positive electrodeactive material layer 31 b is formed on one surface of a collector plateand the negative electrode active material layer 32 b is formed on theother surface of the collector plate.

The power-generating element 30 can be provided by stacking a pluralityof bipolar electrodes. The separator 33 is placed between two bipolarelectrodes adjacent to each other in the stacking direction. Thepositive electrode tab and the negative electrode tab are placed on bothends of the power-generating element 30 in the stacking direction. Partof the positive electrode tab and part of the negative electrode tabprotrude to the outside of the cell case. A laminate film can be used,for example, as the cell case.

The region in which the positive electrode active material layer 31 b isopposed to the negative electrode active material layer 32 b with theseparator 33 interposed between them corresponds to the region in whicha chemical reaction is performed during charge and discharge of the cell1 (hereinafter referred to as a reaction region R). When the lithium-ionsecondary battery is used as the cell 1, lithium ions move in thereaction region R based on charge or discharge.

Since a width W2 of the negative electrode active material layer 32 b islarger than a width W1 of the positive electrode active material layer31 b in the present embodiment, a width WR of the reaction region R isequal to the width W1 of the positive electrode active material layer 31b. Alternatively, the width W1 of the positive electrode active materiallayer 31 b may be larger than the width W2 of the negative electrodeactive material layer 32 b. In this case, the width WR of the reactionregion R is equal to the width W2 of the negative electrode activematerial layer 32 b.

FIG. 4 is a front view of part of the negative electrode plate 32 and isan enlarged view of a region A shown in FIG. 3.

The negative electrode active material layer 32 b is formed by applyingthe constituent material (including the negative electrode activematerial) of the negative electrode active material layer 32 b onto thesurfaces of the collector plate 32 a. The constituent material of thenegative electrode active material layer 32 b is applied onto thecollector plate 32 a along a direction indicated by an arrow D in FIG.4. The collector plate 32 a extends in the direction indicated by thearrow D, and FIG. 4 shows part of the negative electrode plate 32(collector plate 32 a). When the constituent material of the negativeelectrode active material layer 32 b is applied onto the collector plate32 a, a waveform may be produced on an edge E of the negative electrodeactive material layer 32 b. The waveform on the edge E results fromvariations in the width of the applied constituent material of thenegative electrode active material layer 32 b. The edge E is one end ofthe negative electrode active material layer 32 b in the width directionand is located adjacently to the region of the collector plate 32 a thatis to be connected to the negative electrode tab 24.

Wmax shown in FIG. 4 indicates the position of the edge E where thenegative electrode active material layer 32 b has the largest width inthe range of a length L. Wmin indicates the position of the edge E wherethe negative electrode active material layer 32 b has the smallest widthin the range of the length L.

A difference ΔW between the largest width Wmax and the smallest widthWmin corresponds to a (maximum) variation of the width W2 of thenegative electrode active material layer 32 b. The widths Wmax and Wmin,and the variation ΔW are determined in the range of the length L of thenegative electrode plate 32. The length L can be set as appropriate. Forexample, the length L can be set to be larger than the width W2 of thenegative electrode active material layer 32 b. If the variation ΔW ispresent in the range of the length L, the waveform is produced on theedge E of the negative electrode active material layer 32 b. When thelength L is extremely small, it is difficult to determine whether or notthe waveform is produced on the edge E.

In the present embodiment, the variation ΔW is set as described later inthe state in which the waveform is produced on the edge E of thenegative electrode active material layer 32 b, thereby enablingsuppression of variations in capacity among a plurality of cells 1 orsuppression of a reduction in the capacity of the cell 1. The length Lis only required to be set to a length in which the presence of thewaveform on the edge E can be identified.

As shown in FIG. 4, an edge F of the reaction region R is located on theinner side than the edge E of the negative electrode active materiallayer 32 b. The edge F corresponds to one end of the reaction region Rin the width direction of the negative electrode active material layer32 b.

In the present embodiment, as shown in FIG. 3 and FIG. 4, the waveformis produced only on the edge E located at the one end in the widthdirection of the negative electrode active material layer 32 b. The edgelocated at the other end in the width direction of the negativeelectrode active material layer 32 b is formed along the edge (instraight line) of the collector plate 32 a. Alternatively, the waveformmay be produced on the edges located at both ends in the width directionof the negative electrode active material layer 32 b.

FIG. 5 shows experiment results when the variation ΔW of the width W2 ischanged. The vertical axis in FIG. 5 represents a variation of capacityand an average capacity. The variation of capacity refers to a (maximum)variation of capacity among the plurality of cells 1. The variation ofcapacity can be measured with a method described below.

First, the plurality of cells 1 having the variation ΔW at a specificvalue are manufactured, and the capacities of those cells 1 aremeasured. Each of the cells 1 is fully charged and then is discharged ata predetermined rate, so that the capacities of the cells 1 can bemeasured. Next, the cell 1 having the largest capacity and the cell 1having the smallest capacity are specified, and the difference betweenthe (maximum) capacity and the (minimum) capacity is calculated toobtain the variation of capacity. When the value of the variation ΔW ischanged, the variation of capacity can be obtained in association witheach value of the variation ΔW.

The average capacity refers to an average value of the capacities of theplurality of cells 1. The average capacity can be measured with a methoddescribed below.

First, the plurality of cells 1 having the variation ΔW at a specifiedvalue are manufactured, and the capacities of those cells 1 aremeasured. The measurement of the capacities of the cells 1 is performedin the same manner as that described above. After the measurement of thecapacity of each of the cells 1, the average value of the capacities ofthe plurality of cells 1 is calculated to obtain the average capacity.When the value of the variation ΔW is changed, the average capacity canbe obtained in association with each value of the variation ΔW.

The horizontal axis in FIG. 5 represents a ratio (ΔW/Wn) between thevariation ΔW and the width Wn of the negative electrode active materiallayer 32 b. The variation ΔW is defined as the variation of the width W2of the negative electrode active material layer 32 b in the range of thelength L of30 cm. While the length L is set to 30 cm in the experimentresults shown in FIG. 5, the present invention is not limited thereto.The length L may be larger than 30 cm or may be smaller than 30 cm. Thelength L is preferably equal to or larger than 10 cm.

The width Wn refers to a width (set value) in which the constituentmaterial of the negative electrode active material layer 32 b isapplied. In the experiment shown in FIG. 5, the constituent material ofthe negative electrode active material layer 32 b is applied onto thecollector plate 32 a by using the die coater.

In the die coater, the constituent material of the negative electrodeactive material layer 32 b is released from an ejection port of a dietoward the collector plate 32 a. When a distance (referred to as a diegap) between the ejection port of the die and the collector plate 32 ais changed, the width Wn of the negative electrode active material layer32 b can be changed. When the die gap is widened, the width Wn of thenegative electrode active material layer 32 b can be increased. When thedie gap is narrowed, the width Wn of the negative electrode activematerial layer 32 b can be reduced.

On the other hand, when the die gap is widened in the range in which thewidth Wn is obtained, the variation ΔW is easily increased. When the diegap is narrowed in the range in which the width Wn is obtained, thevariation ΔW is easily reduced. In the experiment shown in FIG. 5, thedie gap is changed to change the variation ΔW and to change thevariation ratio (ΔW/Wn).

As shown in FIG. 5, when the variation ratio (ΔW/Wn) is lower than 0.03,the variation of capacity is increased. When the variation ratio (ΔW/Wn)is equal to or higher than 0.03, the variation of capacity does not tendto increase. As the variation ratio (ΔW/Wn) is lower, the edge E of thenegative electrode active material layer 32 b is closer to a straightline.

The edge E of the negative electrode active material layer 32 b isformed in the waveform rather than a straight line to allow the negativeelectrode active material layer 32 b to be easily impregnated with theelectrolytic solution. When the negative electrode active material layer32 b is easily impregnated with the electrolytic solution, variations incapacity among the plurality of cells 1 can be suppressed.

For manufacturing the cell 1, the positive electrode plate 31, thenegative electrode plate 32, and the separator 33 are stacked and thenthe stack is impregnated with the electrolytic solution. The easyimpregnation of the negative electrode active material layer 32 b withthe electrolytic solution can suppress variations in the amount of theimpregnation of the electrolytic solution into the negative electrodeactive material layer 32 b. Since the amount of the electrolyticsolution impregnated into the negative electrode active material layer32 b influences the capacity of the cell 1, the suppression ofvariations in the amount of the impregnation of the electrolyticsolution can avoid variations in capacity among the plurality of cells1.

As described above, the cell 1 of the present embodiment can be used asthe assembled battery mounted on the vehicle. In the assembled batteryhaving the plurality of cells 1, variations in capacity among theplurality of calls 1 may adversely affect charge and discharge controlof the assembled battery. For example, the charge and discharge of theassembled battery may be controlled by setting the cell 1 having thesmallest capacity as the reference. In this case, the cells 1 havingcapacities larger than that of the reference cell 1 each have a portionwhich does not contribute to the charge and discharge of the assembledbattery, so that all of the cells 1 can not be efficiently charged ordischarged. When variations in capacity among the plurality of cells 1are suppressed as in the present embodiment, all of the cells 1constituting the assembled battery can be efficiently charged anddischarged.

On the other hand, as shown in FIG. 5, when the variation ratio (ΔW/Wn)is higher than 0.056, the average capacity is reduced. When thevariation ratio (ΔW/Wn) is equal to or lower than 0.056, the averagecapacity does not tend to reduce, and the average capacity can bemaintained at a predetermined value or larger.

When the variation ratio (ΔW/Wn) is higher than 0.056, the edge E of thenegative electrode active material layer 32 b has larger projections anddepressions. When the edge E has the larger projections and depressions,and lithium ions move to the region along the edge E of the negativeelectrode active material layer 32 b, especially to the region of thenegative electrode active material layer 32 b with a larger width, thenthe lithium ions do not return to the reaction region R easily. In thecell 1, charge and discharge are performed by the lithium ions moving inthe reaction region R.

When the lithium ions move to the region out of the reaction region R,the lithium ions can not contribute to the charge and discharge, and thecapacity of the cell 1 is reduced. Especially, when the projections anddepressions of the edge E are extremely large, the lithium ions movingto the region along the edge E are difficult to return to the reactionregion R. Thus, the variation ratio (ΔW/Wn) is set to be 0.056 or lowerto allow even the lithium ions moving to the region along the edge E tobe returned easily to the reaction region R. This can suppress thereduction in the capacity of the cell 1.

As described above, the variation ratio (ΔW/Wn) is preferably setbetween 0.03 and 0.056. More preferably, the variation ratio (ΔW/Wn) canbe set between 0.03 and 0.04. This can suppress the variations incapacity among the plurality of cells 1 or suppress the reduction in thecapacity of the cell 1.

When the constituent material of the negative electrode active materiallayer 32 b is applied onto the collector plate 32 a by using the diecoater, the die gap is first set to a predetermined value. The settingof the die gap to the predetermined value can set the width Wn of thenegative electrode active material layer 32 b. After the constituentmaterial of the negative electrode active material layer 32 b is appliedonto the collector plate 32 a, the variation ΔW is measured in the rangeof the length L. The variation ratio (ΔW/Wn) is calculated from thewidth Wn as the set value (fixed value) and the variation ΔW, and it isdetermined whether or not the variation ratio (ΔW/Wn) satisfies thecondition of the following expression (1).

0.03≦ΔW/Wn≦0.056   (1)

When the variation ratio (ΔW/Wn) does not satisfy the condition of theexpression (1), the die gap is adjusted. Since widening the die gapeasily increases the variation ratio, the die gap can be widened whenthe variation ratio (ΔW/Wn) is lower than 0.03. On the other hand, whenthe variation ratio (ΔW/Wn) is larger than 0.056, the die gap can benarrowed.

In this manner, the variation ΔW can be adjusted in the process ofmanufacturing the negative electrode plate 32 such that the variationratio (ΔW/Wn) satisfies the condition of the expression (1).

While the die coater is used in the experiment shown in FIG. 5, thepresent invention is not limited thereto, and any device may be used aslong as the variation ΔW can be adjusted. For example, the gravurecoater can be used instead of the die coater. In the gravure coater, theconstituent material of the negative electrode active material layer 32b is held in a (engraved) groove formed in a surface of a gravure roll.Then, the collector plate 32 a is brought into contact with the surfaceof the gravure roll, so that the constituent material of the negativeelectrode active material layer 32 b can be applied onto the surface ofthe collector plate 32 a.

When the gravure coater is used, an experiment can be previouslyperformed to cause the variation ratio (ΔW/Wn) to satisfy the conditionof the above expression (1). For example, it is possible to set therotation speed of the gravure roll or the shape of the groove formed inthe surface of the gravure roll as appropriate such that the variationratio (ΔW/Wn) satisfies the condition of the above expression (1).

While attention is focused on the variation ratio (ΔW/Wn) of thenegative electrode plate 32 in the present embodiment, the presentinvention is not limited thereto. Specifically, a variation ratio in thepositive electrode plate 31 can be set as in the present embodiment(expression (1)). Since the positive electrode plate 31 is formed byapplying the constituent material of the positive electrode activematerial layer 31 b onto the collector plate 31 a, the variations in thewidth of the positive electrode active material layer 31 b can beadjusted with the same method as in the present embodiment. In otherwords, it is only required that the variation ratio (ΔW/Wn) shouldsatisfy the condition of the expression (1) in at least one of thepositive electrode plate 31 and the negative electrode plate 32.

Of the separator 33, the positive electrode active material layer 31 b,and the negative electrode active material layer 32 b, the separator 33is most easily impregnated with the electrolytic solution. The positiveelectrode active material layer 31 b is next easily impregnated with theelectrolytic solution. The negative electrode active material layer 32 bis least easily impregnated with the electrolytic solution. Thus, whenthe variation ratio (ΔW/Wn) of the negative electrode active materiallayer 32 b is set to satisfy the condition of the expression (1), theimpregnation of the electrolytic solution into the negative electrodeactive material layer 32 b can be efficiently achieved.

It is contemplated that the time for the impregnation of theelectrolytic solution is extended in order to impregnate the negativeelectrode active material layer 32 b with the electrolytic solution.However, as the time for the impregnation of the electrolytic solutionis longer, the collector plate 32 a of the negative electrode plate 32may be dissolved. Thus, the time for the impregnation of theelectrolytic solution can be shortened by easily impregnating thenegative electrode active material layer 32 b with the electrolyticsolution in the manner described in the present embodiment.

1. An electric storage apparatus comprising: a positive electrode plateand a negative electrode plate each having an active material layer, theactive material layer containing an electrolytic solution and beingformed in a predetermined width on a partial region of a collectorplate; and a separator placed between the positive electrode plate andthe negative electrode plate and containing an electrolytic solution,wherein, at least one of the positive electrode plate and the negativeelectrode plate, an edge of the active material layer in a widthdirection has a waveform, and a set value Wn of the width of the activematerial layer and a variation ΔW of the width of the active materiallayer satisfy a condition of the following expression (I):0.03≦ΔW/Wn≦0.056   (I).
 2. The electric storage apparatus according toclaim 1, wherein the width of the active material layer of the negativeelectrode plate is larger than the width of the active material layer ofthe positive electrode plate, and the active material layer of thenegative electrode plate satisfies the condition of the expression (I).3. The electric storage apparatus according to claim 2, wherein a regionof the active material layer of the negative electrode plate that isopposed to the active material layer of the positive electrode plate isnot adjacent to the edge.
 4. The electric storage apparatus according toclaim 1, wherein the edge is located at a position in the collectorplate that is adjacent to a region in which the active material layer isnot formed.
 5. A method of manufacturing an electric storage apparatuscomprising the steps of: forming an active material layer in apredetermined width on a partial region of a collector plate tomanufacture a positive electrode plate and a negative electrode plate;placing a separator between the positive electrode plate and thenegative electrode plate; and impregnating the active material layer ineach of the positive electrode plate and the negative electrode plateand the separator with an electrolytic solution, wherein, inmanufacturing at least one of the positive electrode plate and thenegative electrode plate, a waveform is formed on an edge of the activematerial layer in a width direction, and a set value Wn of the width ofthe active material layer and a variation ΔW of the width of the activematerial layer are set to satisfy a condition of the followingexpression (II),0.03≦W/Wn≦0.056   (II).
 6. The method of manufacturing the electricstorage apparatus according to claim 5, wherein a constituent materialof the active material layer is applied onto a surface of the collectorplate by using a die coater.
 7. The method of manufacturing the electricstorage apparatus according to claim 5, wherein the width of the activematerial layer of the negative electrode plate is larger than the widthof the active material layer of the positive electrode plate, and theactive material layer of the negative electrode plate satisfies thecondition of the expression (II).
 8. The method of manufacturing theelectric storage apparatus according to claim 7, wherein the edge isformed at a position in the active material layer of the negativeelectrode plate that is not adjacent to a region opposed to the activematerial layer of the positive electrode plate.
 9. The method ofmanufacturing the electric storage apparatus according to claim 5,wherein the edge is formed at a position in the collector plate that isadjacent to a region in which the active material layer is not formed.10. The electric storage apparatus according to claim 3, wherein theedge is located at a position in the collector plate that is adjacent toa region in which the active material layer is not formed.
 11. Themethod of manufacturing the electric storage apparatus according toclaim 8, wherein the edge is formed at a position in the collector platethat is adjacent to a region in which the active material layer is notformed.